/// <summary>
/// Predict all unknown values as global mean rating.
/// </summary>
public string RunGlobalMean()
{
if (!ReadyForNumerical)
{
GetReadyForNumerical();
}
StringBuilder log = new StringBuilder();
log.AppendLine(Utils.PrintHeading("Global Mean"));
// Prediction
Utils.StartTimer();
double globalMean = R_train.GetGlobalMean();
DataMatrix R_predicted = R_unknown.Multiply(globalMean);
log.AppendLine(Utils.StopTimer());
// Numerical Evaluation
log.AppendLine(Utils.PrintValue("RMSE", RMSE.Evaluate(R_test, R_predicted).ToString("0.0000")));
log.AppendLine(Utils.PrintValue("MAE", MAE.Evaluate(R_test, R_predicted).ToString("0.0000")));
return(log.ToString());
}